Quercetin, an antioxidant pigment in apples, onions, green and black tea and other plants, reduced viral illness and maintained physical and mental abilities in physically stressed athletes in a new study funded by the U.S. Department of Defense. Researchers from Appalachian State University in Boone, North Carolina, recruited 40 trained cyclists and randomly assigned 20 to take 1,000 mg of quercetin, plus niacin and vitamin C per day for five weeks, while the remaining 20 took a placebo. Researchers included niacin and vitamin C to help absorb the quercetin.

After three weeks, the athletes rode bicycles for three hours per day on three consecutive days to the point of exhaustion. Researchers took blood and tissue samples and determined that the cyclists had high levels of stress hormones, oxidative stress and significant muscle damage. Following the extreme exercise, 45% of the cyclists in the placebo group reported illness compared to 5% of those in the quercetin group with no side effects. The immune benefit did not appear until after the exercise. Lead researcher, Dr. David Nieman remarked, “It appears that it takes significant stress to bring out quercetin’s infection-fighting properties.”

Researchers also administered mental alertness and reaction-time tests at the point of exhaustion and found that the quercetin group performed measurably faster than placebo. Doctors noted that this is the first controlled clinical trial to show that a plant compound reduced viral infection and plan to follow up with a study on psychological stress in the general public. The average diet contains 25 to 50 mg of quercetin per day.

Reference: Southeastern Regional Meeting of the American College of Sports Medicine; February, 2007, Charlotte, North Carolina.

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